The invention relates generally to the area of programmable machines and specifically discloses a method and apparatus for synchronizing the operation of a machine element with a workpiece which is experiencing a measurable unprogrammed change of position with respect to the machine.
There is significant current development in the area of programmable industrial manipulators. These devices have great versatility and may be employed in relatively simple operations, e.g. loading and unloading workpieces, painting, welding, assembling, etc. Industrial manipulators are generally designed to operate in conjunction with a stationary workpiece. However, to maintain the economies of many industrial environments, it is necessary that a manipulator operate in conjunction with a workpiece as it is found in the existing industrial environment. This substantially increases the complexity of the problem. Generally, when manipulators are programmed, the relative position of the manipulator to the workpiece is fixed. However, in many industrial enviroments, the position of the workpiece relative to the manipulator may change during the execution of a program.
One example of the above situation is the requirment that a machine execute a program of operations while the workpiece is moving past the machine on a conveyor. The prior art illustrates several solutions to this problem. One solution shown is to mount the machine on a moving base, and the motion of the moving base is synchronized with the conveyor motion by electrical, hydraulic or mechanical means. In a second solution, the machine remains stationary; but the conveyor motion is programmed during a dry cycle. Therefore, during the execution of the program, the machine operation is coordinated with the conveyor motion. Finally, one solution illustrates programming the machine by a lead through method while the conveyor is moving, therefore, the conveyor motion is inherently part of the program.
A stationary base machine is disclosed which responds to unprogrammed changes in relative position between the machine and workpiece. However, the disclosed invention is applicable to any machine regardless of its configuration. Further, the disclosed invention can compensate for any measurable unprogrammed change in relative position between the machine and workpiece. Further, the invention is not dependent on the location of a measuring device detecting the unprogrammed change in relative position.